Available online at ScienceDirect · List of words for each one of the conditions RB (Resh ‘ר’ in the beginning of the word), RE (Resh in the end), SB (Samech ‘ס’ in the
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c o r t e x 5 9 ( 2 0 1 4 ) 7 4e8 3
Available online at
ScienceDirect
Journal homepage: www.elsevier.com/locate/cortex
Research report
Decoding letter position in word reading
Ori Ossmy a,b, Michal Ben-Shachar c,d and Roy Mukamel a,b,*
a Sagol School of Neuroscience, Tel-Aviv University, Ramat-Aviv 69978, Israelb School of Psychological Sciences, Tel-Aviv University, Ramat-Aviv 69978, Israelc The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan 52900, Israeld English Department, Linguistics Division, Bar-Ilan University, Ramat-Gan 52900, Israel
a r t i c l e i n f o
Article history:
Received 28 January 2014
Reviewed 31 March 2014
Revised 19 May 2014
Accepted 3 July 2014
Action editor Roberto Cubelli
Published online 25 July 2014
Keywords:
Reading
fMRI
Pattern analysis
Letter position
Abbreviations: LPD, letter position dysleintraparietal sulcus; MVPA, multivariate pattvector machine; FDR, false discovery rate; B* Corresponding author. School of PsychologE-mail address: [email protected]
spatial aspects of word recognition (Cohen et al., 2008;
Vinckier et al., 2006) and in visual feature binding (Shafritz
et al., 2002; Xu, 2007) are also recruited in binding letters to
relative position when reading Hebrew words.
Although the VWFA has been found to be involved in
readingwords in this study andmanyprevious ones (Dehaene,
2009), we did not find significant classification accuracy in this
region with respect to letter position. A previous study using
machine learning has reported that fMRI activity in VWFA al-
lows significant classification of word position in visual space
and that classification levels increase when adding informa-
tion from the rVWFA (Rauscheker, Bowen, Parvizi, &Wandell,
2012). These results suggest that these regions encode spatial
information at the whole word level. Our results suggest that
relative to L-IPS, the VWFA is less suited for encoding relative
letter positions within a word, in agreement with previous
claims about its holistic nature (Glezer et al., 2009). Our func-
tional connectivity results support the idea of a ‘cross-talk’
between the dorsal and ventral streams regarding letter posi-
tion. These results are consistent with a recent study by Vogel,
Miezin, Petersen, and Schlaggar (2012) demonstrating func-
tional connections between VWFA and left IPS, and other
studiesproviding evidence for structural connectivity between
the two areas (Ben-Shachar, Dougherty, & Wandell, 2007;
Yeatman, Rauschecker, &Wandell, 2013).
Reading Hebrew words places an unusual burden on letter
position encoding since transposing two adjacent letters in a
written Hebrew word is very likely to produce a different real
word. This means that binding letters to their relative posi-
tions within a word is critical for correct recognition, unlike
the situation in many non-semitic orthographies. Future
studies will be necessary to assess whether the left parietal
involvement in letter position encoding generalizes to other
orthographies.
Our results shed new light on the neural mechanism un-
derlying LPD. LPD is a reading impairment in which patients
mistake the word ‘board’ for ‘broad’ or the word ‘trial’ for
‘trail’. Friedmann and Gvion (2001) reported two Hebrew-
speaking patients with acquired LPD who suffered a left
Occipito-Parietal lesion. This dyslexia was also reported in its
developmental form (Friedmann & Rahamim, 2007; Reilhac,
Jucla, Iannuzzi, Valdois, & D�emonet, 2013), yet there is no
study that has isolated the neural substrate underlying LPD.
Our study is the first to show brain imaging data in healthy
subjects supporting a left parietal mechanism for letter posi-
tion encoding. If indeed left parietal abnormality correlates
with an LPD diagnosis, it raises the exciting possibility of using
fMRI pattern analysis for diagnostic purposes.
Finally, it is an open question whether successful letter
position encoding in the L-IPS will generalize to other posi-
tions, e.g., internal letter positions that are known to be less
sensitive to transpositions, at least in Indo-European lan-
guages (Perea & Lupker, 2003; But see Frost, 2012). Further-
more, based on neuropsychological data, we expect this
encoding to be neurally dissociated from similar processes
applied to other stimuli such as digits or musical notes (Dotan
& Friedmann, 2007). Future neurophysiological studies could
exploit the current strategy to explore the role of L-IPS in
processing relative position under broader conditions
including different letters, lexical status or orthographies.
Acknowledgments
This study was supported by the Israeli Center of Research
Excellence (I-CORE) in Cognition (I-CORE Program51/11), Israel
Science Foundation (grants No. 1771/13 and 2043/13), Human
Frontiers Science Project (HFSP) Career Development Award
(CDA00078/2011-C) to R.M., US-Israel Binational Science
Foundation (BSF award #2011314 to M.B.-S.) and Sagol School
of Neuroscience fellowship to O.O. The authors thank Ariel
Krasovsky for providing the initial code for the searchlight
algorithm.
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